Apparatus for maintaining constant force between a finishing tool and a workpiece

ABSTRACT

An apparatus for maintaining constant force engagement between a finishing tool and a workpiece. The apparatus includes a motor supported on a rotatable base. A tool holder coupled to the motor supports a finishing tool at as point offset from a rotational axis of the base. The apparatus further includes an actuator configured to rotate the base, whereby the finishing tool is caused to engage the workpiece with a constant and known force.

FIELD OF THE INVENTION

[0001] The present invention pertains to the finishing of manufactured goods, and more particularly to an apparatus for maintaining a constant force between a finishing tool and a workpiece.

BACKGROUND OF THE INVENTION

[0002] In the manufacture or restoration of various products, it is often desirable to perform a finishing operation, such as buffing, grinding or polishing. For example, in the manufacture or restoration of fine jewelry, it is often desired to buff precious metal components to achieve a fine finish for aesthetic appearance. During such finishing operations, it is generally important not to apply excessive pressure of the finishing tool against the workpiece, which would otherwise cause unwanted excessive removal of material from the workpiece. Optimally, it is desired to maintain contact between the workpiece and the finishing tool at a known and constant force.

[0003] Prior devices for maintaining a constant force between a finishing tool and a workpiece have typically involved complex mechanical structures, often incorporating electronic controls and feedback. Aside from an increased likelihood of malfunctioning, the complexity of these prior devices generally results in an increased cost, often to the point that use of the devices is prohibitive for economic reasons. By way of example, an automated finishing system might utilize a programmable computer-controlled robotic arm to engage a workpiece against a stationary finishing tool with a constant force. Such a configuration generally requires some type of force feedback to an appropriately programmed controller, as well as complicated programming code necessary to manipulate the robotic arm to engage the workpiece with a constant force. The time, effort, and equipment necessary to achieve the desired result of constant force finishing with this type of system is likely to increase the cost to an extent that use of such a device is prohibited in many applications.

[0004] There is thus a need for a simple apparatus for maintaining a constant force between a finishing tool and a workpiece which overcomes drawbacks of the prior art, such as those described above.

SUMMARY OF THE INVENTION

[0005] The present invention provides an apparatus for maintaining constant force engagement between a finishing tool and a workpiece. Advantageously, the apparatus facilitates efficient finishing of a workpiece by assuring that an adequate, but not excessive force is maintained against the workpiece by the finishing tool, regardless of variation of positioning of the workpiece relative to the tool, surface irregularities of the workpiece, or wear of the finishing tool. In an exemplary embodiment, the apparatus includes a motor supported on a rotatable base and coupled to a tool holder for supporting a finishing tool at a point offset from the rotational axis of the base. The rotatable base is coupled to an actuator configured to rotate the base and thereby cause the finishing tool to engage a workpiece. Advantageously, the actuator can be controlled to maintain a constant and known force between the finishing tool and the workpiece.

[0006] In one aspect of the invention, the actuator is a pneumatic or hydraulic cylinder that is coupled to the base by a cable. The cylinder is coupled to a source of pressurized air or fluid that may be controlled to cause a piston of the cylinder to apply a constant and known force to the cable, whereby the finishing tool is caused to engage the workpiece with a constant force.

[0007] In another aspect of the invention, the actuator is coupled to the rotatable base by a gear train. In one exemplary embodiment, the gear train comprises a rack and pinion, and the actuator is a pneumatic or hydraulic cylinder coupled to the rack. According to this embodiment, the pinion is coupled to the rotatable base whereby movement of the cylinder piston causes the base to rotate such that the finishing tool engages the workpiece with a constant force.

[0008] In another aspect of the invention, the gear train comprises a bull and pinion. The actuator comprises a rotary pneumatic or hydraulic device and is coupled to the pinion gear. The bull gear is coupled to the rotatable base, whereby actuation of the rotary device causes the base to rotate such that the finishing tool engages the workpiece with a constant force.

[0009] In yet another aspect of the invention, the actuator comprises a weight coupled to the rotatable base by a cable routed over a pulley. The weight may be selected to cause the base to rotate and engage the finishing tool against the workpiece with a constant force proportional to the weight.

[0010] The features and objectives of the present invention will become more readily apparent from the following Detailed Description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

[0012]FIG. 1 is a perspective view of an exemplary apparatus for maintaining constant force engagement between a finishing tool and a workpiece according to the present invention;

[0013]FIG. 2 is a perspective view of another exemplary embodiment of an apparatus according to present invention;

[0014] FIGS. 3A-3B are perspective views of additional exemplary embodiments of an apparatus according to present invention; and

[0015]FIG. 4 is a perspective view of yet another exemplary embodiment of an apparatus according to the present invention.

DETAILED DESCRIPTION

[0016] Referring to FIG. 1, there is shown an exemplary apparatus 10 a for maintaining a constant force engagement between a finishing tool and a workpiece. The apparatus 10 a includes a motor 12 supported on a rotatable base 14. In the exemplary embodiment shown, base 14 comprises a support surface 16 mounted upon a vertical column 18 that is rotatably coupled to a footplate 20, whereby support surface 16 may be rotated about an axis 17 extending axially along vertical column 18. The apparatus further includes a finishing tool 22, such as a buffing, grinding, or polishing wheel, operatively coupled to the motor 12 by a tool holder 24, such as a collet or chuck. As the finishing tool 22 is driven by motor 12, actuator 26 a rotates the base 14 to bring the finishing tool 22 into contact with a workpiece 28 to thereby perform finishing operations on the workpiece 28.

[0017] While the finishing tool 22 has been depicted in the exemplary embodiments herein as a disk or wheel coupled for rotational movement to motor 12 by tool holder 24, it will be understood by those of ordinary skill in the art that finishing tool 22, tool holder 24, and motor 12 may have various other configurations for finishing a workpiece, as known in the art. As a non-limiting example, the finishing tool may comprise a belt coupled to the motor for vibratory, orbital, or oscillatory motion. It will also be recognized that, while the various embodiments shown and described herein depict finishing tool 22 coupled for rotation about an axis having a substantially perpendicular orientation with respect to rotational axis 17, finishing tool 22, along with tool holder 24 and motor 12, may alternatively be configured for rotation about an axis parallel to axis 17, or even oblique to axis 17, provided finishing tool 22 is offset from axis 17.

[0018] In the exemplary embodiment shown in FIG. 1, workpiece 28 is supported by a robotic arm 30 and gripped by an end effector 32, but it will be recognized by those skilled in the art that workpiece 28 may alternatively be manually supported, or supported by other known devices for engagement with finishing tool 22. Actuator 26 a comprises a pneumatic cylinder 33 having a piston 34 coupled to base 14 by a cable 36, whereby movement of the piston 34 causes support plate 16 to rotate relative to footplate 20. The pneumatic cylinder 33 is coupled to a source of pressurized air (not shown) by hoses 40, 42. A pressure regulator 38 is provided intermediate the cylinder 33 and the source of pressurized air and has a control knob 44 to permit adjustment of the tension applied to cable 36 by piston 34, whereby finishing tool 22 may be caused to contact workpiece 28 with a known force. Advantageously, the tension applied through the cable 36 by pneumatic cylinder 33 is maintained substantially constant such that the force between the finishing tool 22 and the workpiece 28 remains constant regardless of variation in positioning of the workpiece by robot arm 30, wear of the finishing tool 28, or variation in the surface of the workpiece 28.

[0019] FIGS. 2-4 illustrate other embodiments of the present invention utilizing various mechanisms for actuating rotatable base 14 to move finishing tool 22 into contact with workpiece 28, in a manner similar to that described above for FIG. 1. In these embodiments, the motor 12, support surface 16, finishing tool 22, and tool holder 24 are the same as described above for FIG. 1 and these components shown in phantom for illustrative purposes.

[0020] Referring now to FIG. 2, there is shown another exemplary apparatus 10 b for maintaining constant force contact between a finishing tool and a workpiece. In this embodiment, actuator 26 a again comprises a pneumatic cylinder 33, however piston 34 is coupled to rotatable base 14 by a rack and pinion gear train. Specifically, rack 50 is coupled to the piston 34 and engages pinion gear 52 coupled to base 14, whereby linear movement of piston 34 under control of pressure regulator 38 causes support surface 16 to rotate. Rotation of support surface 16 in turn moves finishing tool 22 into contact with a workpiece 28. Accordingly, pressure regulator 38 may be adjusted by manipulation of knob 44 to control the movement of piston 34 such that finishing tool 22 is maintained in engagement against workpiece 28 with a known and constant force, as described above.

[0021] Referring now to FIG. 3A, there is shown another exemplary apparatus 10 c of the present invention. In this embodiment, actuator 26 b comprises a weight 54 and a pulley 56 coupled to rotatable base 14 by cable 36. Weight 54 maintains constant tension in cable 36 to cause base 14 to rotate, thereby bringing finishing tool 22 into contact with workpiece 28 in a manner similar to that described above for FIG. 1. It will be recognized that weight 54 can be varied to apply any desired force to cable 36 such that a known and constant force can be maintained between finishing tool 22 and workpiece 28.

[0022]FIG. 3B illustrates another exemplary apparatus 10 d of the present invention, similar to that shown in FIG. 3A, but wherein actuator 26 c comprises a constant force spring that is coupled to rotatable base 14 by cable 36. Accordingly, the constant force spring may be selected to provide a desired tension in cable 36 such that finishing tool 22 is maintained in constant force contact with workpiece 28.

[0023] Referring to FIG. 4, there is shown yet another exemplary apparatus 10 e of the present invention. In this embodiment, actuator 26 d comprises a rotary pneumatic device 60 coupled to rotatable base 14 by a bull and pinion gear train. As shown in FIG. 4, rotary pneumatic device 60 is connected to a source of pressurized air (not shown) by hoses 62, 64 coupled through a pressure regulator 66 with control knob 67. A pinion gear 68 fixed to the output shaft of the rotary pneumatic device 60 engages a bull gear 70 coupled to rotatable base 14 such that rotation of pinion gear 68 by the rotary pneumatic device 60, actuated by the pressurized air, causes rotatable base 14 to move finishing tool 22 into contact with workpiece 28. Accordingly, pressure regulator 66 may be adjusted such that rotary pneumatic device 60 applies a known torque to rotatable base 14 through pinion gear 68 and bull gear 70 so that finishing tool 22 engages workpiece 28 with a known constant force.

[0024] While actuators 26 a and 26 d have been described as pneumatic devices, it will be understood that the actuators may alternatively be hydraulic devices operating under the action of fluid pressure. In such embodiments, pressure regulators 38 would be adapted to regulate fluid pressure, as known in the art.

[0025] While the present invention has been illustrated by the description of the various embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of the general inventive concept. 

What is claimed is:
 1. An apparatus for maintaining constant force engagement between a finishing tool and a workpiece, the apparatus comprising: a base mounted for rotation about an axis of rotation; a motor supported on said base; a tool holder operatively coupled to said motor and configured to receive the finishing tool and to support the finishing tool at a point offset from the rotational axis of said base, whereby the finishing tool is driven by said motor; and an actuator coupled to said base and configured to rotate said base to engage the finishing tool against the workpiece at a constant force.
 2. The apparatus of claim 1, wherein said actuator comprises a linear hydraulic cylinder.
 3. The apparatus of claim 1, wherein said actuator comprises a linear pneumatic cylinder.
 4. The apparatus of claim 1, wherein said actuator comprises a rotary pneumatic device.
 5. The apparatus of claim 1, wherein said actuator comprises a rotary hydraulic device.
 6. The apparatus of claim 1, wherein said actuator comprises a spring configured to apply a constant force to said base.
 7. The apparatus of claim 1, wherein said actuator comprises a weight coupled to said base.
 8. The apparatus of claim 1, wherein said actuator is operatively coupled to said base by a gear train.
 9. The apparatus of claim 8, wherein said gear train comprises a rack gear and a pinion gear.
 10. The apparatus of claim 8, wherein said gear train comprises a bull gear and a pinion gear.
 11. The apparatus of claim 1, wherein actuator is operatively coupled to said base by a cable. 